Sometimes I like to shoot for comfort, technical wear, the right food, sunglasses for the job, etc.
Other times I just want to remember what it's like to experience that child-like feeling of just grabbing your bike and rushing out for a ride.
There's something really liberating and fun about not acting like an adult and preparing. And it re-introduces some risks that make the ride more 'interesting'... such as whether you'll bonk, and whether you get lost because you didn't plan, or whether it rains and you get soaked to the bone as you didn't check.
Jeans or not, if you ride enough, often enough, hard enough, and long enough, you will
* Bonk.
* Get lost.
* Get soaked/frozen because the weather took a turn for the worse.
* Get roasted/bathed in sweat because it got a lot warmer than you planned on.
I have hours of anecdotes for all of the above, despite dressing in the best possible gear I had/could afford at the time, and riding the best possible bicycle I could afford at the time (gears, brakes, etc...).
On the other hand, in my defence, ... no, there's no defence.
Will be doing it again though, it was hella fun.